http://www.amb.org/audio/alpha10/ http://www.amb.org/audio/alpha10/ Here's another arduino-based pre-amp. This one includes relay-based stepped attenuators an

http://www.amb.org/audio/alpha10/ http://www.amb.org/audio/alpha10/ Here's another arduino-based pre-amp. This one includes relay-based stepped attenuators and input selectors. The pcbs are all available as well as the schematics in case you just want to use it as a base for your own project.